Heat dissipation substrate, heat dissipation circuit board, heat dissipation member, and method for manufacturing heat dissipation substrate

A heat dissipation substrate comprising a metal material provided adjacent to one surface of an insulating layer, wherein

• a material of the metal material contains copper or a copper alloy, or aluminum or an aluminum alloy, and the metal material has a sheet shape having a thickness of 0.2 mm or more and 20 mm or less,
• the insulating layer includes:
• a first insulating layer provided adjacent to the metal material;
• and
• a second insulating layer provided adjacent to a surface of the first insulating layer on a side opposite to the metal material,
• the first insulating layer and the second insulating layer are metal oxide layers different from each other,
• the first insulating layer is a metal oxide layer containing 90 wt % or more of an aluminum oxide represented by a composition formula 1:
• AlxOyCz (where Al represents an aluminum atom, O represents an oxygen atom, and C represents a carbon atom;
• x, y, and z denote a weight ratio, x+y+z=100, x is 30 or more and 50 or less, y is 40 or more and 60 or less, and z is 3 or more and 25 or less) and having a thickness of 0.01 μm or more and 0.2 μm or less and a porosity of 10% or less, and
• the second insulating layer is a metal oxide layer containing 95 wt % or more of an aluminum oxide represented by a composition formula 2:
• AlxOyCz (where Al represents an aluminum atom, O represents an oxygen atom, and C represents a carbon atom;
• x, y, and z denotes a weight ratio, x+y+z=100, x is 30 or more and 55 or less, y is 40 or more and 65 or less, and z is 0 or more and 10 or less) and having a thickness of 0.3 μm or more and 30 μm or less and a porosity of 10% or less.